Quantification of 1-(propan-2-ylamino)-4-propoxy-9H-thioxanthen-9-one (TX5), a newly synthetized P-glycoprotein inducer/activator, in biological samples: method development and validation.

A simple, rapid and economical method was developed and validated for the analysis and quantification of 1-(propan-2-ylamino)-4-propoxy-9H-thioxanthen-9-one (TX5), a P-glycoprotein inducer/activator, in biological samples, using reverse-phase high-performance liquid chromatography (HPLC). A C18 column and a mobile phase composed of methanol-water (90/10, v/v) with 1% (v/v) triethylamine, at a flow rate of 1 mL/min, were used for chromatographic separation. TX5 standards (0.5-150 µm) were prepared in human serum. Methanol was used for TX5 extraction and serum protein precipitation. After filtration, samples were injected into the HPLC apparatus and TX5 was quantified by a conventional UV detector at 255 nm. The TX5 retention time was 13 min in this isocratic system. The method was validated according to ICH guidelines for specificity/selectivity, linearity, accuracy, precision, limits of detection and quantification (LOD and LOQ) and recovery. The method was proved to be selective, as there were no interferences of endogenous compounds with the same retention time of TX5. Also, the developed method was linear (r2 ≥ 0.99) for TX5 concentrations between 0.5 and 150 µm and the LOD and LOQ were 0.08 and 0.23 µm, respectively. The results indicated that the reported method could meet the requirements for TX5 analysis in the trace amounts expected to be present in biological samples.

Determination of 21 photoinitiators in human plasma by using high-performance liquid chromatography coupled with tandem mass spectrometry: A systemically validation and application in healthy volunteers.

In the present study, a comprehensive and sensitive method for simultaneous determination of 21 PIs (nine benzophenones, eight amine co-initiators, and four thioxanthones) in human plasma using high-performance liquid chromatography coupled with tandem mass spectrometry was developed and validated. Two different pre-treatment approaches (liquid-liquid extraction (LLE) and LLE coupled with solid-phase extraction (SPE)) and eight extraction solvents were studied to optimize sample treatment to obtain good recoveries and reduce any matrix effects. The procedure of LLE+SPE was selected as final sample treatment procedure because it obtained higher recoveries as well as lower matrix effects than that performed by LLE alone. The recoveries of 21 target analytes at three spiked concentrations (0.05, 0.5, and 5 ng/mL) ranged from 81% to 109%. The intra- and inter-day relative standard deviations were between 2.5% and 13%. Accuracy and precision data indicated that the detection method was accurate and precise for most of the PIs. The linearities of the labeled dilution calibration curves at 10 concentration levels (iLOQ to 100 ng/mL or iLOQ to 200 ng/mL) were good with correlation coefficients ranged from 0.995 to 0.999. The method quantification limits were in the range of 1.7-16 pg/mL. The analytical method was applied to the analysis of PIs in 14 human plasma samples collected from pregnant women in Guangdong Province, China. Fifteen PIs were detected with total concentrations ranging from 318 to 2772 pg/mL. The ubiquitous contamination of human plasma with PIs suggests that there is widespread exposure to these compounds. Consequently, there should be increased awareness of these pollutants in the environment.

Pharmacokinetic studies in mice of two new thioxanthenones (183577 and 232759) that showed preferential solid tumor activity.

Two new thioxanthenones, 183577 and 232759, have rekindled interest in the development of representatives from this class of structures as useful anticancer agents. Although the mechanism of action is unknown, both compounds demonstrated a similar spectrum of solid tumor selectivity. 232759 was selected for clinical development because it showed no hepatotoxicity in preliminary studies, whereas 183577 showed hepatotoxicity but only at the maximum tolerated dose (MTD). The limiting toxicity for the clinical candidate was myelosuppression in preliminary studies. Plasma and tissue drug levels, as well as protein binding, were studied in mice using optimal administration times at the MTD for each drug (for 183577, this was a 4-h infusion at 1350 mg/m2 and for 232759, it was a 5-min injection at 240 mg/m2), as well as at one-half the MTD for the clinical candidate. The drugs were 96-100% bound by plasma proteins. The peak drug concentrations, half-life, and area under the concentration-time curve in plasma for 183577 were 3483 ng/ml, 465 min, and 2018 microgram/ml. min, respectively. The peak drug concentration, half-life, and area under the concentration-time curve in plasma for 232759 were 5257 ng/ml, 44 min, and 276 microgram/ml. min, respectively, at the MTD and 2810 ng/ml, 40 min, and 110 microgram/ml. min at one-half the MTD. In all instances of simultaneous measurements, drug concentrations were equal or higher in tissues than they were in plasma. Unlike the plasma and kidney concentrations of 183577, the liver concentrations did not show a declining trend over the 8-h observation period. Declines in plasma, liver, kidney, and tumor levels of 232759 were detected over the 8-h observation period. The sustained high 183577 concentration in liver is believed to be responsible for its prolonged half-life and hepatotoxicity. Evidence for metabolism of the parent drugs was based on the finding of additional peaks on the high-pressure liquid chromatography tracings. Future studies will focus on identification and antitumor studies of these presumed metabolites in hopes of a better understanding of the solid tumor activity profiles and toxic effects of these compounds.

Serum concentrations of the isomers of clopenthixol and a metabolite in patients given cis(Z)-clopenthixol decanoate in viscoleo.

Cis(Z)-clopenthixol decanoate in Viscoleo (Sordinol Depot, Cisordinol Depot, Clopixol Inj.) was given intramuscularly to nine schizophrenic patients with dosage intervals of 1 or 2 weeks. Serum concentrations of the two geometric isomers of clopenthixol and its N-dealkyl metabolite were recorded in two successive dosage intervals. Significant correlations were found for dose vs area under the serum concentration curve and vs serum concentrations measured on individual days. The last mentioned concentrations are good measures of the area under the serum concentration curve, which expresses the drug load of the patient. The serum concentration curves in two successive dosage intervals were very similar. Maximum serum concentration was seen 5-7 days after injection and the mean maximum/minimum fluctuation was 1.6 with the 2-week dosage interval. The finding of very low amounts of the trans(E)-isomers of clopenthixol and the N-dealkyl-metabolite shows that isomerization of the cis(Z)-compounds into the corresponding trans(E)-isomers does not take place within the organism.

Comparison of serum levels after intramuscular injections of 2% and 10% cis(Z)-flupentixol decanoate in Viscoleo to schizophrenic patients.

The serum concentrations of cis(Z)-flupentixol after injection of 2% and 10% cis(Z)-flupentixol decanoate in Viscoleo (Depixol injection, Fluanxol Depot) have been investigated in a crossover study with eight schizophrenic patients. No statistically significant difference was found between the two preparations when the data from individual days or areas under the serum concentration curves were considered. For the individual patients a difference was found between the two treatments in six cases; one preparation gave the higher serum concentration in four cases and the other preparation in two cases. Thus, the difference found within individual patients reflects the intraindividual variation rather than a difference between preparations. The maximum serum concentration was seen at 4 or 7 days after injection. The maximum/minimum fluctuation ratio indicates that dosage intervals longer than 2 weeks seem reasonable for most of the patients. The similarity in the serum concentrations, no matter which concentration of flupentixol decanoate solution was given, indicates that a dispersal and possibly a metabolic breakdown of the oil depot takes place in the muscle.

Serum concentrations of cis(Z)-flupentixol and prolactin in chronic schizophrenic patients treated with flupentixol and cis(Z)-flupentixol decanoate.

Nine chronic schizophrenic patients selected from three hospital departments were treated with flupentixol (orally and IV) and cis(Z)-flupentixol decanoate in Viscoleo (IM) in a three-phase pharmacokinetic study. Oral administration (single and repeated dosage) showed a relatively slow absorption with maximum serum concentration around 4 h after administration. Intravenous injection indicated multicompartment kinetics for cis(Z)-flupentixol. The biological half-lives calculated after the different doses were the same, indicating that the pharmacokinetics of cis(Z)-flupentixol does not differ between single and repeated administration and does not change when moderately higher doses are given. The bioavailability of orally administered cis(Z)-flupentixol was calculated to be about 40% with IV injection as reference. After IM administration maximum serum concentration was seen between 4 and 10 days in most patients. Calculation of a disappearance half-life gave very variable results, indicating that the release of the drug from the oil depot is not a monoexponential process. The intramuscular depot had a much lower bioavailability than IV injection, which means that steady state has not been obtained after 8 weeks of depot treatment. Serum prolactin concentrations were elevated during neuroleptic treatment, but no correlation was found between prolactin concentrations and the serum concentrations of cis(Z)-flupentixol. A correlation between the changes in clinical ratings and concentrations of cis(Z)-flupentixol or prolactin was not found.

A depot neuroleptic withdrawal study. Plasma concentration of fluphenazine and flupenthixol and relapse frequency.

A double-blind withdrawal trial in 41 chronic schizophrenic outpatients was carried out during 6 months. Depot neuroleptics (fluphenazine decanoate or flupenthixol decanoate) were compared with placebo to evaluate clinical and neurological effects during continued therapy and during withdrawal. The drugs were significantly more effective than placebo in preventing relapse and rehospitalization. In the placebo group 62% relapsed compared to 27% in the drug group. There was a weak and nonsignificant tendency to a higher relapse frequency in the flupenthixol group compared to the fluphenazine group. After withdrawal for 6 months, plasma levels for fluphenazine were detectable. Plasma levels for flupenthixol were not detectable after 9 weeks of withdrawal. The differences in the plasma levels may possibly explain the difference in relapse rate between the two depot neuroleptics. Furthermore, it was found that the patients who relapsed during fluphenazine treatment had a significantly lower plasma level of the drug than patients who did not relapse during treatment. The results from this study provide some information on the therapeutic levels of fluphenazine and flupenthixol in schizophrenic patients.

Blood and plasma kinetics of cis(Z)-clopenthixol and fluphenazine in psychiatric patients after intramuscular injection of their decanoic esters.

Whole blood and plasma concentrations of active neuroleptic drugs were measured in eight schizophrenic outpatients who had received cis(Z)-clopenthixol decanoate in Viscoleo or fluphenazine decanoate in sesame oil by intramuscular injection. Whole blood and plasma concentrations were very similar, though there was a slight tendency for blood concentrations to be higher than plasma concentrations. Maximum concentrations appeared at 1 week after administration of cis(Z)-clopenthixol decanoate, whereas the highest concentrations after fluphenazine decanoate were seen at the end of the 3-week dosage interval. Some between-individual variation and a limited within-individual variation was seen.

Fluorimetric determination of some thioxanthene derivatives in dosage forms and biological fluids.

A simple and highly sensitive method is proposed for the fluorimetric determination of four thioxanthene derivatives, namely: chlorprothixene, clopenthixol, flupentixol and thiothixene, in dosage forms and biological fluids. The method involves the use of nitrous acid as an oxidant to produce the corresponding fluorescent thioxanthenone sulphoxides. The experimental parameters were carefully studied and incorporated into the procedures. The results obtained compare favourably with those obtained by the official methods. The concentration-fluorescence plots were rectilinear over the range of 0.04-0.4 microg/ml for thiothixene, and 0.02-0.25 microg/ml for the other compounds, with minimum detectability (S/N = 2) of 2 ng/ml for all the studied compounds except thiothixene which was 4 ng/ml. The proposed method was applied to the determination of the studied compounds in dosage forms. The results obtained were in good agreement with those obtained adopting the USP XIII method. The proposed method was further applied to the determination of flupentixol in spiked human urine and plasma, the percentage recoveries were 94.39 +/- 1.81 and 96.46 +/- 0.28, respectively. A proposal of the reaction pathway was presented.

Investigation of the binding of various tricyclic neuroleptics and antidepressants to alpha 1-acid glycoprotein.

Recent studies have shown that the interaction of various tricyclic neuroleptics and antidepressants with isolated alpha 1-acid glycoprotein occurs at one common binding site and with relatively high association constants. The aim of the present study was to find differences in the binding of some phenothiazines, thioxanthenes, and several other drugs reported to bind alpha 1-AGP. The findings suggest that the affinity of the phenothiazines and thioxanthenes depends primarily on the existence of the tricyclic skeleton and is generally increased by the basic side chain. Substituents at position 3 of the phenothiazine nucleus influence the affinity in a variable way. The losses of radioactivity by non-specific absorptions to the dialysing chambers were considered for the calculation of the association constants. No correlation between association constants and the antipsychotic potency of neuroleptic drugs could be detected.

Correlation of bioavailability in man with simulated absorption data for three doxantrazole preparations.

The in vitro and in vivo availability of doxantrazole, a potential antiallergic compound has been evaluated. A solution was significantly less bioavailable than either tablet or suspension formulations and it is suggested that this is associated with the large volume of the solution vehicle altering the hydrophilicity of the gastrointestinal fluids. In vitro availability was determined from absorption rate constants and absorption profiles obtained using the Sartorius absorption and solubility simulators. A statistically significant correlation was found between the percentage absorbed in vitro at 1 h and both total urinary recovery and area under plasma curve values in vivo. It is considered that in vitro determination of diffusion through artificial lipid membranes may be a useful predictive method of in vivo availability.

LC/MS determination of bromazepam, clopenthixol, and reserpine in serum of a non-fatal case of intoxication.

Combined liquid chromatography and mass spectrometry (LC/MS) with a moving belt interface can be used as a rapid method for the determination of bromazepam, clopenthixol, and reserpine in serum samples obtained from cases of acute overdoses with combinations of these drugs. Low resolution detection limits are about 100 pg for the three drugs, while in high resolution mode the detection limit for bromazepam is shown to be at least 35 pg. Accurate masses were obtained in a serum sample within 5 ppm using high voltage scanning over a narrow mass range for about 10 ng of bromazepam and clopenthixol, respectively. Chemical deactivation of the belt was shown to effectively reduce memory effects and to improve the desorption characteristics of the belt leading to higher yields of evaporated intact molecules.

Stereoselective disposition of flupentixol: influence on steady-state plasma concentrations in schizophrenic patients.

Steady-state plasma concentrations of cis(Z)-flupentixol (active principle) and trans(E)-flupentixol (inactive) were measured in 41 patients at least on one occasion. Results indicate that concentrations of the trans-isomer are significatively higher. This demonstrates that the two isomers are not handled in the same way by the organism. This may be relevant if plasma level monitoring is performed using non-specific analytical methods.

Radioimmunoassay for flupenthixol in plasma.

We describe a radioimmunoassay for the neuroleptic drug flupenthixol, suitable for routine monitoring of its concentration in blood. Antibodies for the assay were raised in a sheep against a 7-carboxyflupenthixol/ovalbumin conjugate. The resulting assay, with [3H] flupenthixol as the label, is capable of detecting 2.0 microgram of flupenthixol per liter, in a 100-microliter plasma sample. The antiserum shows no cross reactivity with tricyclic drugs and low interference from the major metabolites of flupenthixol. Concentrations in plasma after a single oral dose of flupenthixol have been followed in one volunteer. Peak values were reached after 3 h. Determinations of flupenthixol after fortnightly intramuscular depot injections of the sustained-release preparation, flupenthixol decanoate, showed the extent of fluctuations during this period.

Serum concentrations of cis(Z)- and trans(E)-clopenthixol after administration of cis(Z)-clopenthixol and clopenthixol to human volunteers.

The serum concentrations of cis(Z)- and trans(E)-clopenthixol have been estimated in human volunteers by an HPLC-method after administration of a clopenthixol tablet, which contains the cis(Z)- and the trans(E)-isomers in the ratio 1/2, or a cis(Z)-clopenthixol tablet. The serum concentration curves obtained for the cis(Z)-isomer after administration of the two drug preparations were very similar, and thus independent of the presence of the trans(E)-isomer in one of the preparations. Likewise the biological half-lives and the areas under the serum concentration curves for cis(Z)-clopenthixol were similar after the two preparations. The biological half-life of cis(Z)-clopenthixol was as a mean 20 hours (12-29 hours) indicating that from a pharmacokinetic point of view a dosage interval of 24 hours is possible for most patients. The biological half-life of trans(E)-clopenthixol is found to be longer than that for cis(Z)-clopenthixol.

Serum levels of the isomers of clopenthixol in patients given cis(Z)-clopenthixol or cis(Z)/trans(E)-clopenthixol.

The serum levels of the two geometric isomers of clopenthixol and N-dealkylated clopenthixol were estimated in 9 patients, who received cis(Z)-clopenthixol (Cisordinol, Clopixol tabl.) in one period and the double dose of cis(Z)/trans(E)-clopenthixol (Sordinol, Ciatyl) in another period. Nearly equal concentrations of the neuroleptically active isomer, cis(Z)-clopenthixol, were found in the two periods. This finding is in agreement with the clinical experience, but in disagreement with the administered amounts of cis(Z)-clopenthixol, which were larger when the cis(Z)-isomer was given alone. Highly significant correlations were found between dose and mean serum level of cis(Z)-clopenthixol and between dose and area under the serum concentration curves for 8 of the patients, the ninth patient, who had received additional medication showed deviating results. No indication of transformation of cis(Z)-clopenthixol into trans(E)-clopenthixol or vice versa was found. Trans(E)-clopenthixol was found in the serum samples even after administration for one week with the cis(Z)-clopenthixol tablets indicating a relatively long half-life of the trans(E)-isomer. The cis(Z)-isomer of N-dealkyl clopenthixol was found in about the same concentration as cis(Z)-clopenthixol in both periods, while trans(E)-N-dealkyl clopenthixol occurred in about 4 times higher concentrations in patients who had either been given cis(Z)/trans(E)-clopenthixol before they went into the study or had received it in the first period of this study.